Card Range To Study

23 Cards in this Set

The APU provides bleed air for the ECS, main engine starting and electrical power on the ground and in flight

What has priority, APU electrical loads or pneumatics

Electrical loads take priority over pneumatics

How is the APU cooled

It is cooled by drawing airflow over the APU engine and the oil cooler then exhausting the air

What are the APU operating time limits with the inspection doors open

10 mins with the APU unloaded and 5 mins with it loaded

What is the source and pressure of APU bleed air

The APU bleed air comes from the single stage centrifugal compressor and it normally provides apprx 55 psi

When does the APU oil pass through the APU oil cooler

When the APU oil Temp exceeds a pre-determined higher than normal operating range the oil will be route through the oil Cooller. Below that temp the Oil Cooler is bypassed

Will the APU perform a protective shutdown on the ground for a low oil pressure condition? In flight?

On the ground yes but not in flight

May the APU oil be replenished using the Auto Replenishment System

Yes

How is the APU oil filled manually and can it be overfilled by using this method

By removing the gravity fill cap and filling the until the sight guage indicates full. It will overflow and therefore cannot be overfilled manually

How many EGT probes are fitted to the APU engine

2 probes connected to a single temp sensing unit

Should an APU speed sensor fail, what are the cockpit indications? If the 2nd sensor then fails, what will occure to the APU in flight

If either RPM sensor fails, the APU FAULT advisory message will be triggered and the APU will continue to operate normally. If both sensors fail the APU will auto shutdown and a restart would be inhibited

What is the effect of te APU EGT probe failure(s)

Loss of one probe has no effect
Loss of both probes on the grnd will induce an auto shutdown
Loss of both probes in flight will not cause an auto shutdown

What is the purpose of the SCV (surge control valve) and when does it function

To control APU surge potential when operating under electrical load at altitudes above 16,375 ft

When can the APU accept an electrical load in flight and on the ground

2 seconds after the APU reaches 99% RPM. ELectrical loading is not available if the RPM drops below 95%